In order to improve the effectiveness and functionality of wound dressings and surgical implants, various attempts have been made to incorporate them with a variety of medicaments such as antibiotics, analgesics, and the like—see U.S. Pat. No. 5,972,366.
Examples of antibacterial wound dressings are disclosed in U.S. Pat. No. 4,191,743 to Klemm et al., U.S. Pat. No. 2,804,424 to Stirn et al., and U.S. Pat. No. 2,809,149 to Cusumano. Similarly, U.S. Pat. No. 3,987,797 to Stephenson discloses a suture rendered antimicrobial.
Dressings which attempt to promote wound healing are disclosed in U.S. Pat. No. 5,124,155 to Reich. Many prior art surgical bandages and dressings which incorporate medications are made by soaking the material in an aqueous solution of the medicine. This can render the carrier brittle and inflexible upon drying. Moreover, it is difficult to control the rate of release of the medicament, or its effect on peripheral tissues, when it is applied to the carrier dissolved in a liquid state. Also, many important medicines are water insoluble and cannot be applied by this technique. Alternatively, the medicament is applied to the dressing or implant as a powder or dust which is quickly released and possesses a danger that large drug particles may irritate tissue or enter the circulatory system where they can block capillaries.
In addition to externally applied dressings, it is also known to impregnate an implantable surgical material with a medicament. For example, U.S. Pat. No. 5,197,977 to Hoffman Jr. et al. disclose a synthetic vascular graft that is impregnated with collagen and a medicament.
Additionally, Boyes-Varley et al. in Int. J. and Maxillafac. Surg. 1988; 17:138-141, describe the use in an animal study of a the Gelfoam® brand sponge with a saline solution of medicaments. However, the Physicians' Desk Reference, (Medical Economics, Co., Oradell, N.J.) 1992 edition warns that “it is not recommended that Gelfoam® be saturated with an antibiotic solution or dusted with antibiotic powder.” A similar warning is provided with the entry of another popular surgical implant—the Surgicel® brand absorbable hemostat—which states that “the Surgicel® hemostat should not be impregnated with anti-infective agents.”
One well known method of suppressing infection is to provide relatively high levels of an antibiotic systemically. For example, high levels of gentamicin are systemically administered to patients in order to prevent infection in high risk situations, such as patients subjected to severe trauma whose wounds may well have been compromised with infectious bacteria. High systemic levels can have adverse effects including loss of hearing. Another method employed is to dissolve an antibiotic such as gentamicin in a solution such as water and spray the wound thoroughly with the solution. In some situations the solution is so dilute as to be ineffective in preventing infection. Accordingly, another alternate method which is employed is to simply put high concentrations of gentamicin powder into the wound. High concentrations applied locally are known to hinder bone healing. Further, although high concentrations can be applied the powder may not last sufficiently long in order to prevent infections after a considerable amount of time has passed. Accordingly, there remains a need for a formulation which can avoid the problem of high level systemic administration and provide for local administration at sufficient levels over a sufficiently long period of time so as to suppress infection.
In view of such the present invention is proposed.